3D Urban Modeling

GEOG 40323

April 3, 2018

Three-dimensional coordinate systems

  • Z-coordinates: vertical measurements (elevation), or measurement of magnitude

Vertical datums

  • Reference for measuring heights/elevation
  • Common vertical datums:
  • Mean sea level
  • The geoid (orthometric heights)

Digital elevation models (DEMs)

  • Raster representation of a terrain’s (commonly the Earth’s) surface

Applications of DEMs

  • Shaded relief mapping
  • Surface analysis and modeling
  • Hydrologic modeling

Triangulated irregular networks (TINs)

Source: qgis.org

LiDAR

  • Light Detection and Ranging
  • Laser pointed at Earth; returned light analyzed to provide information about elevation, vegetation, etc.

How LiDAR works

Source: Penn State

How LiDAR works

  • LiDAR systems can record different ‘returns’ with each pulse that reflect different features

Source: Penn State

LiDAR examples

  • The Ballpark at Arlington

Source: TNRIS

LiDAR examples

  • Six Flags over Texas

Source: TNRIS

LiDAR data formats

  • Historically, LiDAR stored in ASCII text files
  • Industry standard: LAS files (binary format)
  • LiDAR in ArcGIS: the LAS dataset

Tech advances: LiDAR and UAVs

3D GIS concepts

  • Extrusion: vertical stretching of a 2D shape for display in 3D, based on some attribute or value

  • Base heights: how elevation/height values are defined within a three-dimensional GIS view

  • Drape: display of a layer in three dimensions given the defined base heights

Building footprints

  • Geographic data representing outline of a building
  • Example on Google Maps

Buildings in 3D

  • Building footprints can be extruded based on their recorded heights
  • Multipatch polygons: 3D features with multiple shapes encoded

Source: aubreyrhea.net

3D in ArcGIS: 3D Analyst

Source: Esri

3D in ArcGIS

  • ArcGIS Pro: Native 3D visualization

Let’s try it out!

3D cities: CityEngine

3D cities: CityEngine

Urban 3D applications